1. Field of the Invention
The present invention relates to an electroconductive polymer suspension solution, an electroconductive polymer material, and an electrolytic capacitor and a method for producing the same.
2. Description of the Related Art
Electroconductive polymer materials are used for electrodes of capacitors, electrodes of dye-sensitization solar cells and the like, electrodes of electroluminescence displays, and the like. Electroconductive polymers obtained by polymerizing pyrrole, thiophene, 3,4-ethylenedioxythiophene, aniline or the like are known as the electroconductive polymer material.
The above-mentioned electroconductive polymer can be obtained by chemical oxidation polymerization method or electropolymerization method. In late years, since an electroconductive polymer material can easily be obtained, for example, as disclosed in JP 2005-123630 A, there is great interest in a method in which an electroconductive polymer material are formed by applying an electroconductive polymer suspension solution on a substrate such as a condenser body of an electrolytic capacitor, and by drying it.
JP 2005-123630 A discloses an electrolytic capacitor in which an electroconductive polymer material is applied to a solid electrolyte and a polymer outer layer. In JP 2005-123630 A, an electroconductive polymer material, which is composed of an electroconductive polymer particle (polythiophene), a polyanion and a binder, is used as a solid electrolyte or a polymer outer layer, to realize a reduction of an ESR (equivalent series resistance) and a leakage current of the electrolytic capacitor.
The electroconductive polymer material disclosed in JP 2005-123630 A is composed ° fan electroconductive polymer particle, a polyanion and a binder, and the composition results in improving adhesiveness with a condenser body and reducing an ESR. However, in the composition of JP 2005-123630 A, since the connection between electroconductive polymer particles is weak, the connection between electroconductive polymer particles is likely to be broken by a time-related deterioration by heat or stress, which results in a problem that the electroconductivity as the electroconductive polymer material is reduced. Therefore, electrolytic capacitors using a conventional electroconductive polymer material in a solid electrolyte have a problem that the ESR is raised by a time-related deterioration.
Thus, in order to solve the above-mentioned problem, the object of the present invention is to provide an electroconductive polymer suspension solution and an electroconductive polymer material which has a high electroconductivity and in which the time-related deterioration of the electroconductivity is suppressed. Also, the object of the present invention is to provide an electrolytic capacitor with a low ESR using the electroconductive polymer material as a solid electrolyte and a method for producing the same.